How many miles on a bike is equivalent to running??

Lets say I do 25 miles on the bike per day. what would that be equivalent to running?

It depends. Mountain bike or road bike? Terrain? Wind? What do you mean by equivalent - calories burned/work? equivalent time?

On one hill climb that I used to do a lot (1.7 miles, 800ft gain?), my best time on a bike was 10:46 and my best time running was around 13-14 minutes at the same effort (threshold for both, probably hurt more on the bike though). So around 1.25 miles bike to 1 mile run. On steeper climbs and off road, it could be that running a climb is easier than riding it. In cyclocross, you are running and carrying or pushing the bike on the steep run ups, so you definitely work a lot harder there than if you were just running.

Headwinds can be killer on a bike. Pedaling into a 20 mph headwind, you probably work about as hard as if you were running.

On the flats with no wind in a standard position on a road bike, maybe 7:30/mile (8 mph) pace running would be effort wise (guesstimating) 20-22 mph, so maybe 2.6 miles bike to 1 mile run. But how often do people ride in these conditions? I usually bike on the hills, rolling backcountry roads, or off road.

Downhills: I once did 7.5 miles in 12 minutes (37.5 mph average) going down a long descent in Yosemite, doing almost no work. The same 7.5 miles running would have taken, say 50-55 minutes at an easy pace. The ratio would be something like an infinite number of bike miles to 1 mile running.

You don't have impact when you bike, so you can generally get many more training hours a week on the bike than running, even if working at the same effort.

Not sure about the equivalence in terms of calorie burning or working the cardio system. But there is no substitute for running in the end. Cycling and running use very different muscles and in very different ways, so biking can definitely help your running as a supplement, but not as a replacement.

Most people say 3-4 miles of biking is = to 1 mile of running. Uphills are similar (like that poster said 1:1.25). Downhills, you really don't count that because it's basically no cardiovascular effort other than technical skill. The flats is like a 5:1 ratio unless you are really hammering and/or battling a headwind.

Perhaps you could try your own test using a heart rate monitor.

Warm up until your hear rate is at a steady 120 beats per minute (or whatever). Then run a mile at that pace and time it.

On a road bike set on a turbo trainer (static roller wheel) get to the same heart rate, hold the pace and heart rate, and see what the speedo is showing.

If the mile run was 6 minutes = 10mph

If the bike was at 24 mph then ratio is 2.4 bike to 1 mile.

"If the bike was at 24 mph then ratio is 2.4 bike to 1 mile."

That doesn't make sense. What if I was going 15 mph? Would the ratio be 1.5 bike to 1 miles? So the slower I go the more miles I cover equivallently?

I have a relative who is a state champion masters cyclist.

When he was running, a few years back, I could kick his arse by 10 minutes in a half Marathon.We are the same age and trained together.He is 145lbs and I am 175+.On the Bike I can not keep him in sight.

ESD2 is the closest,

Cycling is equal to exactly one half of running, so inversely you would double cycling times if all conditions were created equal. (this is nearly impossible)

I believe Texas Southern did a research project on this very subject

Biking miles are biking miles. Running miles are running miles. Attempting to equate them is a waste of time.

Log the biking miles as biking miles and be done with it.

I agree with that dude above me. It's really ridiculous to try and compare the two.

If the 2:1 ratio is accepted, then why don't they bike 52.2 miles in an Ironman, instead of the 100+ miles they do? Is the bike portion a tougher leg in an Ironman?

him wrote:

I agree with that dude above me. It's really ridiculous to try and compare the two.

If the 2:1 ratio is accepted, then why don't they bike 52.2 miles in an Ironman, instead of the 100+ miles they do? Is the bike portion a tougher leg in an Ironman?

No. Formulas that you can put miles biked x some factor to = miles run are bullshit. A linear equation will not work. If one were to say 4 miles biked=1 run then an easy 5 mile run = 20 miles on the bike. But Going up 20 more on the bike, then twenty more, many times over is not the same as adding 5 more to the run. Going from 80 to 100 miles on a bike is not very hard. Especially when compared to going from 20 to 25 miles run. Once you ride over a few hours and if you keep eating it is not very hard to go longer.

true, I did a 12 hour time trial on a bike and it was no harder than a Marathon.

4 to 1 or close to that (bike to run)

i suspect there is no linear relationship as well.

putting aside that bikes and runs work the body a bit different, my guess is closer to 5 or bike miles to 1 mile run. in galloways 1st book of running (no ref there to walk breaks in that book if that matters) i think he says 5-1, but notes no real science to support it and that this was based on talking to buddies and his experience.

I heard for every six miles on a bike, its equivilant to one mile running

I do not know the answer to this question.

him wrote:

I agree with that dude above me. It's really ridiculous to try and compare the two.

If the 2:1 ratio is accepted, then why don't they bike 52.2 miles in an Ironman, instead of the 100+ miles they do? Is the bike portion a tougher leg in an Ironman?

The Ironman was actually a combination of 3 events that were separate events in Hawaii. The marathon, a 112 mile bike and the ocean swim. That is why the distances are what they are.